Variation in Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) defoliation and mortality caused by the western spruce budworm (Choristoneura occidentalis [Freeman]) was measured in sequential annual surveys of a stand near Pemberton, British Columbia. The implications of this variability in designing defoliation and mortality surveys is discussed.

Surveys of mortality and top-kill caused by the western spruce budworm, Choristoneura occidentalis Freeman, in 65 stands of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco are reported. Top-kill was detected in 85% of the stands and 25% of the trees surveyed. Mortality amounted to 8% and less than 1% of the trees examined in the Vancouver and Kamloops Forest Regions, respectively. Both frequency of top-kill and mortality were related to the number of years defoliation in the stand and were higher on suppressed trees than on dominant or co-dominant trees. Younger stands sustained a higher incidence of topkill than older stands. Tree mortality was higher on steep slopes than on flat terrain. These results suggested that top-kill or mortality were the results of physiological stress on the trees, in addition to the debilitating effects of defoliation.

The mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins) is a native bark beetle and a major disturbance agent in western North American forests. In the 1970s and 1980s, a MPB outbreak occurred in Waterton Lakes National Park (WLNP) in southwestern Alberta. The MPB outbreak resulted in variable levels of mortality of mature lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson), reducing density, volume, and basal area of overstory trees. By 2010, lodgepole pine was proportionally no longer the dominant overstory species, with increases in non-pine conifer and broadleaf species. The MPB susceptibility index decreased in most stands over time, especially in stands with the highest MPB-caused mortality. Downed woody material was characterized by fine and coarse fuel mass and volume, which both increased from 2002 to 2010, and the abundance of coarse fuels was highest in 2010, nearly 30 years after peak MPB activity. Density of understory saplings and small regeneration increased from 2002 to 2010 and was dominated by non-pine conifer and broadleaf species; lodgepole pine was nearly absent. Hierarchical clustering using 2010 MPB susceptibility and composition data characterized biological legacies remaining after the MPB outbreak. These legacies suggest multiple successional trajectories in WLNP dominated by species other than lodgepole pine. The MPB outbreak resulted in greater heterogeneity in composition and structure and suggests that stands have been resilient to this disturbance.

The western spruce budworm (Choristoneura occidentalis Freeman = C. freemani (Razowski), Lepidoptera: Tortricidae) (WSB) is a recurrent defoliator of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and other conifers in western North America. Repeated defoliation causes timber depletions, which often require control using pest management programs involving combinations of aerial sprays with biological controllers (Bacillus thuringiensis) and other tactics. Anticipating the recurrence cycle of this periodic defoliator is important for forest management planning, which needs to consider budworm-caused depletions in timber supply analyses, and for risk management and control. We studied the historical periodicity of outbreaks at the western edge of the insect's distribution, on southern Vancouver Island, British Columbia, using the methods of dendrochronology applied to a living Douglas-fir chronology spanning 734 years (1281-2014 CE) and a floating chronology dating from 1863 to 1528 before the Common Era (BCE). To separate the growth fluctuations due to budworm defoliation from climatic fluctuations in the living chronology, we compared the temporal growth patterns of Douglas-fir with those of the non-budworm host western red cedar (Thuja plicata Donn ex D. Don), which is sympatric with Douglas-fir in this area. We concluded that before the 1930s, outbreaks were frequent, severe, and often spatially synchronized. Following the 1930s, periods of growth reductions indicative of outbreaks were present at the same frequency, but were less severe and not as synchronized as before. We provide evidence to suggest that periodic budworm disturbances on southern Vancouver Island have persisted through the centuries but that this regime has gradually shifted outside its historic range at about 1930. We concluded that although WSB is still present in this setting, population levels have not reached detectable outbreak levels for the last 90 years. We hypothesized that the absence of budworm outbreaks in the last 90 years is a response to the drastic ecosystem changes in this region caused by exploitation and fragmentation of the virgin forests, to possible changes in climate and to the accidental introduction of novel budworm predators into the ecosystem.

There is a growing research interest on studying forest mortality in relation to ongoing climate warming, but little is known about such events in past history. The study of past forest mortality provides valuable information for determining baselines that establish the normal parameters of functioning in forest ecosystems. Here we report a major episode of previously undocumented forest mortality in the late 18th century on the northern Tibetan Plateau, China. The event was not spatially uniform, in which a more severe mortality happened in dryer sites. We used dendrochronology to compare radial growth trajectories of individual trees from 11 sites in the region, and found that many trees showed positive growth trend, or growth release, during 1796-1800 CE. Growth releases are a proxy indicator of stand thinning caused by tree mortality. The growth release was preceded by an almost two-decade long growth reduction. Long-term drought related to weakened North Atlantic Oscillation and frequent El Nino events are the likely factors causing the tree mortality in a large area of the plateau. Our findings suggest that, besides the effect of drought in the late 18th century, large-scale forest mortality may be an additional factor that further deteriorated the environment and increased the intensity of dust storms.

Les forêts dominent le paysage canadien, couvrant plus de la moitié de la superficie de notre pays, s’étendant sur 23 degrés de latitude et 88,5 degrés de longitude et représentant environ 10 p. 100 de la superficie forestière de la Terre. Le mode de vie de beaucoup de nos ancêtres autochtones était, et est toujours, intimement lié aux forêts. Dans ce qui est aujourd’hui le Canada, les premiers colons européens ont façonné des colonies à partir des forêts pour survivre et ont tiré parti de la richesse de biens et services offerte par les forêts. Les liens économiques et sociaux entre le Canada et ses forêts sont encore forts, et les forêts influencent une grande partie de la psyché et du mode de vie au Canada; elles contribuent de manière importante à notre prospérité nationale. Compte tenu de notre richesse en forêts et de l’importance de celles-ci pour l’identité, l’économie et le tissu social du Canada, il n’est pas surprenant qu’une forte tradition de science forestière ait surgi au Canada pour nous aider à comprendre, à utiliser et à protéger nos divers écosystèmes forestiers. Les sciences forestières ont fait l’objet d’un investissement national extraordinaire au cours du siècle dernier, et le Canada est devenu un chef de file mondial respecté et influent dans ce vaste domaine de la science. Depuis le début de la réalisation du vaste potentiel économique des forêts canadiennes, au début du XX siècle, on a aussi pris conscience des menaces qui pèsent sur les forêts, en particulier les incendies de forêt et les insectes, qui pourraient nuire aux aspirations économiques du pays. La Loi sur les insectes nuisibles et les parasites de 1910 a donné lieu à la première attention concertée à l’échelle nationale de l’entomologie forestière; elle a rapidement été suivie par une allocation des ressources pour construire des installations de recherche, embaucher du personnel et financer la recherche sur l’entomologie forestière. Bien sûr, on s’intéressait déjà aux insectes associés aux écosystèmes forestiers du Canada, à partir de la première moitié du XIX siècle, mais la grande partie de cette attention se concentrait tout simplement sur la documentation des espèces et la description des dommages causés aux arbres. Néanmoins, ces activités de description ont fourni les premiers fondements de la taxonomie en appui à l’émergence de l’« entomologie forestière économique ». Le domaine de l’entomologie forestière a une longue et influente histoire au Canada, empreinte de fierté et d’innovation, mais ce domaine de la science n’a jamais été examiné en détail et mis en valeur. À la fin de 2011, le concept de mise sur pied d’un important symposium pour examiner et célébrer l’entomologie forestière au Canada a d’abord été mis à l’essai et a été reçu très positivement par la communauté scientifique canadienne. Même si cet événement n’a pas eu lieu, l’enthousiasme de participants à l’idée d’un symposium pour élaborer une publication célébrant l’entomologie forestière au Canada a conduit à une proposition détaillée, au début de 2013, qui a finalement permis la préparation du numéro supplémentaire actuel de The Canadian Entomologist. Le projet a reçu le soutien généreux de Ressources naturelles Canada – Service canadien des forêts et, avec la patience et la persévérance de tous les acteurs, le résultat donne cet ensemble de 14 articles de synthèse qui mettent en valeur l’entomologie forestière au Canada. On a demandé à chaque auteur de se concentrer sur l’examen de l’état de la science au Canada, demettre en évidence les contributions des entomologistes forestiers canadiens et d’attirer l’attention sur les lacunes et les nouveaux débouchés qui pourraient aider à orienter l’avenir de la science de l’entomologie forestière dans notre pays.

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From the early descriptive work, focussed on documenting the forest insect fauna and the impacts of destructive species, Canadian forest entomology has passed through several distinct phases, each triggered by new societal demands of forests and of forest entomologists. We review the various stages that Canadian forest entomology gone through in the last 100 years. Following the initial descriptive and cataloguing phase, forest entomology entered a pest control or forest protection phase, which eventually evolved into the integrated pest management (IPM) era. Although IPM dominated the forest entomology discourse for at least two decades, this approach is now considered to be narrow and pest-centric and is being superseded by a more holistic approach where the emphasis is on ensuring the health and sustainability of forests at landscape levels. The new trends point away from the "command and control" approach of attempting to eradicate pests or reducing pest damage, and towards working with natural processes in the context of ecosystem management. We indicate several areas where 21st century forest entomology could make a contribution towards the sustainable management of Canadian forests.

Abstract A number of insect species in a variety of families and orders damage early regenerating forests. Successful management of pests of regenerating forests requires detailed information on the natural history of the damaging organism, including the factors that increase risk, and a careful assessment of the risk mitigation options. Decision support systems, in the form of stand models capable of incorporating pest management options are required to guide decisions in terms of the expected yields under various pest management scenarios. In this paper we review research to date on the natural history and damage of the most important insect pests of regenerating forests in Canada and propose a framework for risk assessment. Canadian scientists have been active contributors to the research that advanced this field, from the early descriptive studies, to the development of practical tools to assist industry in managing pests of young forests.

ABSTRACTWildfires and mountain pine beetle (MPB) attacks are important contributors to the development of stand structure in lodgepole pine, and major drivers of its evolution. The historical pattern of these events have been correlated with variation in cone serotiny (possessing cones that remain closed and retain seeds until opened by fire) across the Rocky Mountain region of Western North America. As climate change brings about a marked increase in the size, intensity, and severity of our wildfires, it is becoming increasingly important to study the genetic basis of serotiny as an adaptation to wildfire. Knowledge gleaned from these studies would have direct implications for forest management in the future, and for the future. In this study, we collected physical data and DNA samples from 122 trees of two different areas in the IDF-dk of British Columbia; multi-cohort stands (Cariboo-Chilcotin) with a history of mixed-severity fire and frequent MPB disturbances, and single-cohort stands (Logan Lake) with a history of stand replacing (crown) fire and infrequent MPB disturbances. We used QuantiNemo to construct simulated populations of lodgepole pine at five different growth rates, and compared the statistical outputs to physical data, then ran a random forest analysis to shed light on sources of variation in serotiny. We also sequenced 39 SNPs, of which 23 failed or were monomorphic. The 16 informative SNPs were used to calculate HO and HE, which were included alongside genotypes for a second random forest analysis. Our best random forest model explained 33% of variation in serotiny, using simulation and physical variables. Our results highlight the need for more investigation into this matter, using more extensive approaches, and also consideration of alternative methods of heredity such as epigenetics.

The mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera, Curculionidae), a native insect of North America, periodically reaches population sizes that cause serious economic impact to the forest industry in western North America. The most recent outbreak in British Columbia (BC), Canada, which began in the late 1990s, is only now (2015) abating, after causing unprecedented tree mortality in lodgepole pine (Pinus contorta Douglas ex. Loudon) forests. In this paper, we make use of permanent research plots to report on the condition of lodgepole pine forests in the Chilcotin Plateau of central BC, which underwent two fully documented mountain pine beetle outbreaks. In this region, the first outbreak started in the late 1970s and lasted until the mid-1980s; the second outbreak began in the early 2000s and ended in 2010. We measured the impacts of these outbreaks in terms of tree mortality and describe the characteristics of the legacies that remain following these outbreaks, including survivors in various canopy layers and levels of existing and new regeneration. We provide evidence in support of the existence of postdisturbance legacies that classify into five distinct stand structure types. Abundant regeneration and surviving intermediate canopy layers in most stands indicate that management actions to restock pine stands in this area will not likely be necessary. The information provided by this study is important for estimating future forest development and timber supply and for forest planning and management.

The western spruce budworm (WSB), Choristoneura occidentalis Freeman), a defoliator of conifers in western North America, causes severe timber losses to forests. In British Columbia, Canada, where the main species damaged is Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, outbreaks of C occidentalis have been recorded since 1909. However, there is little information on the frequency of outbreaks of this defoliator for previous centuries. This information is needed to establish baselines defining the historic range of variability of this disturbance, to calculate potential depletions in timber supply from defoliation, and to refine forest management plans. Also, precise estimates of budworm recurrence are needed to assess potential ecosystem changes and possible departures from the historic range of this disturbance due to global warming. We used dendrochronology and time series analysis to determine past frequency of spruce budworm outbreaks in southern BC and found that, since the 1500s, outbreaks have been periodic, with a mean return interval of 28 years (95% Confidence Interval 21-35 years). No data was available before the 1500s. We found the number of outbreaks per century, since the 1800s, was fairly constant, with 3-4 outbreaks per century. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.

The current distribution of forest genetic resources on Earth is the result of a combination of natural processes and human actions. Over time, tree populations have become adapted to their habitats including the local ecological disturbances they face. As the planet enters a phase of human-induced climate change of unprecedented speed and magnitude, however, previously locally-adapted populations are rendered less suitable for new conditions, and 'natural' biotic and abiotic disturbances are taken outside their historic distribution, frequency and intensity ranges. Tree populations rely on phenotypic plasticity to survive in extant locations, on genetic adaptation to modify their local phenotypic optimum or on migration to new suitable environmental conditions. The rate of required change, however, may outpace the ability to respond, and tree species and populations may become locally extinct after specific, but as yet unknown and unquantified, tipping points are reached. Here, we review the importance of forest genetic resources as a source of evolutionary potential for adaptation to changes in climate and other ecological factors. We particularly consider climate-related responses in the context of linkages to disturbances such as pests, diseases and fire, and associated feedback loops. The importance of management strategies to conserve evolutionary potential is emphasised and recommendations for policy-makers are provided. (C) 2014 The Authors. Published by Elsevier B.V.

An outbreak of the western spruce budworm temporarily modifies cellular wood anatomy of stem wood in natural and mature Douglas-fir stands impacting wood quality properties.

The western spruce budworm (Choristoneura occidentalis Freeman; WSB) is a widespread and destructive defoliator of commercially important coniferous forests in western North America. In British Columbia, Canada, Douglas-fir (Pseudotsuga menziesii) is the most prevalent host, and records show that significant outbreaks have primarily occurred in the southern interior over the last century. In the central interior of British Columbia, particularly in the Cariboo Forest Region, the most recent outbreak of western spruce budworm, which is in its second decade, has been severe and widespread. It is perhaps due to this long outbreak, which is unprecedented in duration since detailed surveys began in the 1950s, that there is an anecdotal perception that the western spruce budworm is expanding its range northward into the region, affecting Douglas-fir near the edge of its northern distribution. However, very little is known about the long-term outbreak history of western spruce budworm in the central interior of the province. In this study we used 11 Douglas-fir host chronologies and 2 regional Finns non-host chronologies to reconstruct western spruce budworm outbreaks over a 435-year period. Standard dendrochronological techniques were used to develop tree-ring chronologies at each site and the program OUTBREAK was used to detect outbreak periods. We reconstructed 12 outbreaks starting in early 1600s with a mean return interval of 30 years. Sensitivity analysis illustrated that including light, moderate and severe intensity thresholds modified the number of reconstructed outbreaks, their duration and mean return interval. Sub-regional chronologies based on biogeoclimatic subzones and variants (BEC units), revealed strong synchrony of some outbreak events, but not all. Wavelet analysis of the sub-regional chronologies demonstrated the quasi-periodic behavior of western spruce budworm over the entire record, which averaged 32-years. By reconstructing WSB dynamics over 400 years we demonstrated that outbreaks observed over the last 40 years in the Cariboo Forest Region are not unprecedented. Crown Copyright (C) 2014 Published by Elsevier B.V.

This paper examines the risks associated with forest insect outbreaks in a changing climate from biological and forest management perspectives. Two important Canadian insects were considered: western spruce budworm (WSBW; Choristoneura occidentalis Freeman, Lepidoptera: Tortricidae), and spruce bark beetle (SBB; Dendroctonus rufipennis Kirby, Coleoptera: Curculionidae). This paper integrates projections of tree species suitability, pest outbreak risk, and bio-economic modelling.

Climate warming is causing increases in severity of outbreaks and range expansion in a number of insect pests and diseases. Under these conditions, forest managers should choose the best silvicultural practices to optimize production of timber and ecosystem services, while reducing pest damage to tolerable levels. However, information on the short and long term impacts of key pests, such as mountain pine beetle (MPB) (Dendroctonus ponderosae Hopkins), especially when they occur outside their historical geographical range, is scarce and our ability to predict, pre-empt and react to problems is, therefore, limited. Here we propose a general framework to evaluate the risk and impacts of important forest insects in new habitats, and to identify information gaps when conducting risk assessments. The framework consists of four main steps. The first step of risk assessment under potential range expansion is to identify the factors that promote pest spread and colonization of new environments (hazard). A second step is to determine the area at risk and the potential economic impacts (exposure). The third step is to establish if the forest in the new habitat is susceptible to colonization and pest range expansion (vulnerability). The fourth and final step is to determine the options for risk communication and mitigation. We also illustrate the scope and application of this response framework to decision makers, using, as an example, the potential spread of MPB from its native habitats in BC and Alberta into the boreal forests of Canada, especially with regard to the forests of Quebec. (C) 2013 Elsevier B.V. All rights reserved.